1979 xs650 running issue

[Blood sweat and beards]

Hey everyone! I've tried almost everything I can do and I'm still having an issue. I didn't want to post my issue but I need some guidance! I have a 79 xs I built and I had issues that pamco Pete helped me with before, but this issue is weird. I'll try to sum up everything quick:
79 xs with bs34 carbs, plastic floats, Mikes xs jet kit 145 main, 45 pilot, needle at 3rd position, sea level her in myrtle beach, pamco ignition, upgraded pma, capacitor, Mikes xs pod filters, custom exhaust with custom tips (not straight pipes), 750 miles on new ring and top end rebuild, valves and cam tentioner adjusted properly. Now to my issue...bike runs great, starts first kick. Takes a long time to warm up. But she runs great until 60mph and feels like she is surging and occasionally pops thru exhaust like a fuel cut. Over 60 runs fine, 45-50 runs great at steady throttle but 60-65 doesn't run well at all. At steady throttle it will cut back and pop or cough out the exhaust not carbs. On cold days it's worse, on hot days it may do it twice first ride and not at all second ride. Take the filters off runs great wide open but really crappy steady 25 % throttle. Floats are rights height, rebuild kits installed and I'm at a loss. I check my plugs every 100 miles and they aren't black or super lean. There are a brownish color on the tip and blacker around the bottom ring. I need help because I want to take a long highway ride soon and I need her to run like a top! All input and questions welcome. Thanks guys

 

[TwoManyXS1Bs]

...On cold days it's worse, on hot days it may do it twice first ride and not at all second ride...

Now, there's a sign. Fuel uses heat to vaporize. Without enuff heat, you need more fuel, hence the choke.

So, it sounds like it's telling you that it's lean in that zone...

 

[Blood sweat and beards]

Now, there's a sign. Fuel uses heat to vaporize. Without enuff heat, you need more fuel, hence the choke.

So, it sounds like it's telling you that it's lean in that zone...

Should I raise the needles up a notch? Or should I get the Canadian needles and tubes from Mikes xs and go back down on the jetting?

 

[peanut]

as 2M says it sounds like a lean mixture at that throttle setting but the popping when warmed up could be an exhaust valve setting that is too tight.
There is some interesting conversations around lately regarding slightly looser valve adjustment .
I would suggest that you retorque your head if you haven't already done so, then check and adjust your cam chain tension and then reset your valve settings slightly looser and see if there is any improvement .
A picture of your spark plugs might be helpful.

 

[Blood sweat and beards]

as 2M says it sounds like a lean mixture at that throttle setting but the popping when warmed up could be an exhaust valve setting that is too tight.
There is some interesting conversations around lately regarding slightly looser valve adjustment .
I would suggest that you retorque your head if you haven't already done so, then check and adjust your cam chain tension and then reset your valve settings slightly looser and see if there is any improvement .
A picture of your spark plugs might be helpful.

First picture is left plug and second is right

 

[peanut]

excellent image quality.
Well there is no doubt about it your engine is running rather lean.

The leaner it runs the better it runs to a point ....but the downside is the increase in temperature from the lean mix and surging and hanging idle problems. If you go much leaner you're going to start running into detonation problems

I would say that you really need to be looking for a digestive biscuit sort of colour really rather than grey.

 

[Blood sweat and beards]

excellent image quality.
Well there is no doubt about it your engine is running rather lean.

The leaner it runs the better it runs to a point ....but the downside is the increase in temperature from the lean mix and surging and hanging idle problems. If you go much leaner you're going to start running into detonation problems

I would say that you really need to be looking for a digestive biscuit sort of colour really rather than grey.
View attachment 86748

Thank you for the help! At this point should I raise my needles up one notch to richen it up? I never rider her wide open. I cruise around and fastest speed I go is 65 and I'm usually steady between 25 and 50 percent throttle. So I need that midrange less lean

 

[peanut]

I've not much experience at adjusting needles but if you look at this chart it gives you a good idea of which components you need to look at for the various throttle positions. Mid throttle cruising predominently uses the pilot jet and the jet needle . What is often overlooked is how much of the throttle range the pilot jet and idle mixture screw setting contributes to the mid range . Most folk immediately assume that a larger main jet is needed whereas its only 3/4 to WOT where it is important.

 

[5twins]

If that MikesXS jet kit is the one from Heiden Tuning, it could be the root of the problem. It was developed by Heiden specifically for use on a 750 big bore and with their own specially designed 2-1 exhaust. Most find it doesn't work very well on a near stock 650. I would recommend putting the stock needles back in and dropping the mains to a 137.5 or maybe a 140. The one size larger pilot should be OK. Your pleated style pods are going to hinder your tuning efforts as well. You'll never get it as good as it could be using them.

 

[Blood sweat and beards]

An update from yesterday . After work I adjusted my cam chain tensioner, checked my valves and took the slides out of the carbs. I moved the needle up one notch and made sure everything was seated correctly. I kick started the bike and held the choke for maybe 40 seconds and shut it off. Bike idled on its own for once! Rode it home (15 min ride) and it did not pop or hick up once. Seemed a lot smoother at 60mph. I will check my plugs in 50 miles and ride here a few more times to make sure it doesn't change. Then I can tinker with fine tuning and put on the uni pods I have to see if it helps. Before it ran really crappy with the uni filters on. Thanks for all the help guys! I'll prob be taking out that jet kit soon

 

[5twins]

The bad running with the UNIs could be related to that jet kit or if they are the black foam type, it may be related to what oil you used on them. The black foam is very fine and regular foam filter oil can be too thick for it, clogging them. It's recommended that you use just a simple 50-50 gas and motor oil mix.